1. Field of the Invention
The present invention relates to a method and apparatus for color image forming, and more particularly to a method and apparatus for color image forming capable of effectively forming a quality color image by simplifying maintenance pattern management.
2. Discussion of the Background
As a background, the color image forming apparatus described in Japanese Patent Application Laid-Open No. 2005-91901 is known. The color image forming apparatus described in Japanese Patent Application Laid-Open No. 2005-91901 (hereinafter “background image forming apparatus”) forms density detection patterns on a non-image-formation area of a conveyor belt during continuous printing. The background color image forming apparatus then changes image forming conditions of position detection patterns based on detection results of the density detection patterns. Thus, a positional displacement, which may be caused when toner images of different colors are superposed upon each other, can be suitably corrected while image formation efficiency is increased.
More specifically, in the background color image forming apparatus, the position detection patterns are formed on the conveyor belt with image forming mechanisms of respective colors, and are detected with an image position detector. Then, based on results detected with the image position detector, displacement correction processing is executed to correct the positional displacement.
For the displacement correction processing, density detection patterns are formed on a non-image-formation area of the conveyor belt while image formation is not performed onto a transfer sheet. Then, the density detection patterns are detected with the image position detector. Based on results detected with the image position detector, image forming conditions are determined to form the position detection patterns with the image forming mechanisms during execution of the displacement correction processing.
In the background color image forming apparatus according to the above patent document, a system controller starts positional displacement correction when it receives a permission notification for starting the positional displacement correction from a position adjustment controller. The system controller initially detects a density detection pattern formed on a non-image-formation area of the conveyor belt. The density detection pattern is detected with a reflected light sensor of the image position detector.
However, the above patent document does not describe details relating to a position and a timing at which the density detection pattern is formed. In fact, particular consideration is not paid to the position and timing at which the non-image-area density detection pattern is formed.